1. Field of the Invention
This invention relates generally to semiconductor fabrication. More specifically, the invention relates to producing water for use in the fabrication of semiconductors.
2. Description of the Related Art
Ultra-pure water plays an important role in the fabrication of semiconductors. One such role is the thermal oxidation of silicon, wherein a silicon dioxide (SiO2) film is grown on a silicon substrate by oxidizing the surface of the silicon substrate. Thermal oxidation of silicon proceeds much faster in the presence of water. Thus, the advantages are shorter process time and oxidation at a lower temperature as compared to dry oxidation.
Other examples of uses of ultra-pure water during semiconductor fabrication include repairing gate oxide material damaged during plasma etching via source/drain reoxidation; forming of xe2x80x9chardxe2x80x9d oxides or SiOxNy; accomplishing cell reoxidation of high dielectric materials; wet cleaning/wet etching; in situ chamber cleaning for furnace; LPCVD; PECVD; HDP processing chambers and etch chambers; plasma etching; removing organic material such as in photoresist xe2x80x9cashxe2x80x9d applications; and forming silicon oxides or silicon oxynitrides in steam plasma systems.
Pure water is required in each of these fabrication processes to avoid contaminating the fine integrated circuit devices and wiring. As devices are continually scaled down, purity requirements become even more stringent and important to the fabrication of operable high-speed circuitry.
Accordingly, there is a need for an efficient and reliable process for producing water having a high degree of purity for use in semiconductor fabrication processes.
In accordance with one aspect of the invention, a process of treating semiconductor substrates, including the production of pure water, is disclosed. The process comprises catalytically oxidizing ammonia to form water. The water is then supplied to a semiconductor fabrication process.
In accordance with another aspect of the invention, a method of producing substantially pure water for semiconductor fabrication is disclosed. The method comprises introducing ammonia to a catalytic conversion reactor. The ammonia is then oxidized to form water.
In accordance with another aspect of the invention, an apparatus for producing water is disclosed. The water-producing apparatus comprises a housing surrounding a catalytic material for adsorbing ammonia, a source of ammonia in communication with the housing, a source of oxidant in communication with the housing, and an outlet for reaction products, wherein the outlet is connected to a semiconductor processing apparatus.
A preferred embodiment of the present invention is achieved by reacting, in a water-producing apparatus, ammonia with oxygen in the presence of catalytic material that adsorbs the ammonia and promotes a reactivity of the ammonia with the oxygen, such as metal oxides, ion-exchanged zeolites, noble metals, titanium dioxide, silicon dioxide, and combinations thereof, to form effectively nitrogen and water. The produced water is conveyed to a semiconductor fabrication process to be used by the same. According to a number of embodiments of the invention, the water-producing apparatus can, for example, be a catalytic tube reactor, a fixed bed reactor or a fluidized bed reactor.
The preferred embodiments provide a method and apparatus for advantageously producing water for use in semiconductor fabrication processes without the risk of hydrogen explosions while permitting the production of low overall electrical resistance materials comprised of low oxidation-resistant metal gate electrodes while the semiconductor device is being fabricated. Moreover, the preferred embodiments advantageously do not subject a surface p-channel semiconductor device to excessive boron diffusion.